U.S. patent application Ser. No. 14/686,906 disclosed a system which enabled cloth filters to be properly positioned and manipulated for casting projects, and is incorporated by reference herein. Although this system works well, the problem remains in the art that castings may have undesirable metal protrusions. Additional steps have been identified through experimentation to address this issue.
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term “sand casting” can also refer to an object produced via the sand casting process. Specialized factories called foundries produce sand castings. Production of over 70% of all metal parts occurs via a sand casting process such as vertical molding processes.
High-volume foundries typically use vertical molding processes. Molds form a line allowing pouring of castings one after another. The process blows a molding sand mixture into a molding chamber using compressed air. The process then compresses the molding sand between patterned plates, each of which ultimately forms half of the pattern of the sand mold. Two sand molds pushed together form a complete internal sand cavity that receives the molten metal.
After compression, one of the chamber plates, a swing plate, swings open and the opposite plate, a ram plate, pushes the finished sand mold onto a conveyor. If desired, the process inserts cores into the sand cavity to form holes and recesses in the finished part. The cycle repeats until a chain of finished molds butt up to each other on the conveyor.
During this process, molten metal pours into sand cavities from a receptacle known in the art as a “pour cup” located on the top of each mold and positioned above a channel in the sand mold called the sprue. An automated device called a filter setter places the filter between the pour cup and the sprue inlet. The filter setter moves the filter into position and then injects the filter into the sand mold. The filter print is the area in the sand into which the filter inserts.
It is desirable to decrease the size of the filter print because the filter print and channels entirely fill with metal during the casting process. Metal left behind in the sprue, channels and filter print is excess metal, requiring removal from the part and repurposing.
It is a problem known in the art that repurposing metal recovered from the sprue, channels and filter print is very costly. An important component of a foundry's profitability is its ability to reduce the amount of repurposed metal and the effective “yield” of the metal that goes into the finished part. If a foundry is able to reduce the amount of metal recoverable from the sprue, channels and filter print by 10%, this could increase foundry yield by 2% to 5%.
There several problems associated with filters known in the art. Ceramic filters must be carefully primed or they fracture and introduce fragments in the casting. Ceramic filters are large, requiring correspondingly larger filter prints to hold them in place. Ceramic filters are also relatively expensive.
One solution is to replace ceramic filters with cloth or mesh filters. Cloth filters generally strain molten metal more quickly than ceramic filters. Previous attempts to use cloth filters failed because filter setters could not hold the cloth filters in place, filter setters could not insert the cloth filters properly, the filter coatings could not withstand metal temperatures or the cloth filters were not supported properly to withstand the downforce of the poured molten metal.
Furthermore, foundry workers, many wearing protective gear such as gloves, find difficulty in separating a single cloth filter from a stack for insertion into the filter setter. The patterned plates used to create the sand mold in the prior art are not capable of molding an insertion cavity allowing effective insertion of the cloth filter into the sand mold. Moreover, during pouring of the molten metal, inadequate mold support of the cloth filter can cause the filter to dislodge from the sand mold.
It is desirable to provide a foundry system optimized for using a cloth filter.
When castings cool and harden, they often have excess metal protrusions formed by the metal feed inlet channel. Air hammers, jaws, or heavy mallets can remove these protrusions from the casting, but this will often damage the casting.
Generally, the end of an inlet channel that is closest to the casting is significantly narrower than the rest of the channel, creating a weak spot in the excess metal protrusion to make it easier to remove from the casting. However, having a narrow section in the channel can block the flow of molten metal, especially when the casting is cooling.
There is an unmet need for an alternative method for intricate casting.